1. Field of the Invention
The present invention relates to a technique of creating a backup of data, and more in particular, to an efficient technique applied to a storage system for performing a remote copy by interposing a plurality of lines.
2. Description of the Background Art
As an IT (Information Technology) is introduced into conducting business in an enterprise, important business data are stored in storage devices. In preparation of a large scale of damages such as an earthquake and so on, the enterprise considers a countermeasure such as reserving backups of the business data in a remote place.
However, an amount invested in the IT is limited in small and medium enterprise and thus a remote backup is required to be realized at a low cost. Such request may become satisfactory by using low-cost lines, for example, for a line for connecting a plurality of bases.
However, since, for example, an ADSL which is a low-cost line and is generally used has a low data rate in an upload speed which is important upon transmitting data, when copy data amount increases, a manager is required to lease a higher data rate line. The higher data rate line is expensive, and thus a remote copy function capable of using a plurality of cheap and low-speed lines is demanded.
Therefore, in order to satisfy such demand, data are required to be distributed into a plurality of lines such that a plurality of low-speed lines are bonded for virtual speed-up. For example, Japanese Unexamined Patent Application Publication No. 2004-145855 discloses a method that the remote copy function distributes loads into a plurality of ports.